Fix: Show control buttons on hover only on the displayed stream (montage.js)

This will avoid unnecessary display of buttons when hovering over the "Monitor status" line if it is displayed "Outside bottom"

web/skins/classic/views/js/montage.js

@@ -687,7 +687,7 @@ function initPage() {
   //  $j('#zmMontageLayout').val(getCookie('zmMontageLayout'));
   //}
 
-  $j(".grid-monitor").hover(
+  $j(".monitorStream").hover(
       //Displaying "Scale" and other buttons at the top of the monitor image
       function() {
         const id = stringToNumber(this.id);